Analog system and associated methods thereof

ABSTRACT

Methods and devices are provided for circuits. One device includes an adjustment circuit having an adjustable resistor for modifying a resistance value of a resistive device, the adjustment circuit connected to an adjustment terminal of the resistive device. The resistance value of the adjustable resistor changes, when a voltage or charge on the adjustment terminal of the adjustable resistor is changed. The adjustable resistor is a phase change element with an adjusting terminal to which different voltage values are applied for adjusting a conversion device threshold value.

CROSS-REFERENCE TO RELATED ART

This patent application is a continuation of U.S. patent applicationSer. No. 16/788,201, filed on Feb. 11, 2020, now U.S. Pat. No.10/855,298, which is a continuation of U.S. patent application Ser. No.16/394,975, filed on Apr. 25, 2019, now U.S. Pat. No. 10,601,432; whichis a continuation of Ser. No. 15/789,728 filed on Oct. 20, 2017, nowU.S. Pat. No. 10,298,246; which is a continuation of U.S. patentapplication Ser. No. 15/614,977 filed on Jun. 6, 2017, now U.S. Pat. No.9,831,883; which is a continuation of U.S. patent application Ser. No.15/284,087 filed on Oct. 3, 2016, now U.S. Pat. No. 9,698,803. Thedisclosures of each priority application is incorporated herein byreference in their entirety.

BACKGROUND Technical Field

This disclosure is related to analog to digital and digital to analogconversion.

Related Art

Wireless and wireline communications continue to grow today.Applications in wireless communications today may support multi-modeoperation, utilize large portions of network bandwidth, for example, inUltraWideBand and 60-GHz-band systems, as well as attempt to re-use alicensed spectrum. To support this high-demand environment, a highdynamic range of operation for Analog to Digital Converters (ADCs) isdesirable. Conventional ADCs however are inefficient because they mayconsume a significant portion of wireless communication chips power, forexample, in some instances the ADCs may consume almost ⅓ or more of thetotal available power.

Wireline (or wired) communication systems also continue to demandincrease in data throughput, for example, in Ethernet or next-generationcable modems. Wireline communications supporting the PAM4 (where PAMmeans “Pulse Amplitude Modulation”) modulation standards are beingproposed for high speed serial interconnect, network protocol linklayers for example, Ethernet, InfiniBand, Serial Attached SCSI (SmallComputer System Interface) and Fibre Channel. These applications arealso driving demand for high resolution, high-speed, low power, and lowcost integrated ADCs.

In today's system-on-chip (SoC) implementations, power consumption isone important performance and design parameter. The proliferation ofmobile communication devices and distributed wireless sensor networkshas necessitated development of power-efficient analog, radio-frequencyand digital integrated circuits (ICs). Technology scaling may lower thecost of digital logic and memory and there is an incentive to implementhigh-volume baseband signal processing using the latest availableprocess technology. There is significant interest in using transistorswith minimum channel length and minimum oxide thickness to implementanalog functions, because improved device transition frequency, allowsfor faster operations. However, device scaling may adversely affectother parameters relevant to analog designs. To achieve high linearity,high sampling speed, high dynamic range, with low supply voltages andlow power dissipation in ultra-deep submicron CMOS (ComplementaryMetal-Oxide Semiconductor) technology is a major challenge.

Conventional ADC architectures attempt to achieve high conversions ratesat undesirable high power consumption levels and conversion latency.Continuous efforts are being made to improve performance of ADCs atdesirable power consumption levels.

BRIEF DESCRIPTION OF THE DRAWINGS

The various present aspects now will be discussed in detail with anemphasis on highlighting the advantageous features. These aspects depictthe novel and non-obvious systems and methods for network devices shownin the accompanying drawings, which are for illustrative purposes only.The figures are not intended to depict scale. These drawings include thefollowing figures, in which like numerals indicate like parts:

FIG. 1 is a high level block diagram of an interleaved inverter basedflash analog to digital converter (ADC), according to one aspect of thepresent disclosure;

FIG. 2a is a block diagram of an interleaved inverter based flash ADCwithout temperature compensation, according to one aspect of the presentdisclosure;

FIG. 2b is a block diagram of an interleaved inverter based flash ADCwith device selection temperature compensation, according to one aspectof the present disclosure;

FIG. 2c is a block diagram of an interleaved inverter based flash ADCwith threshold adjustment temperature compensation, according to oneaspect of the present disclosure;

FIG. 2d is a block diagram of an interleaved inverter based flash ADCwith binary output value adjustment temperature compensation, accordingto one aspect of the present disclosure;

FIG. 2e is a block diagram of an interleaved inverter based flash ADCwith conversion time adjustment temperature compensation, according toone aspect of the present disclosure;

FIG. 3a is a circuit block diagram showing an inverter based flash ADCwith device selection, according to one aspect of the presentdisclosure;

FIG. 3b is a circuit block diagram showing an inverter based flash ADCwith threshold programming, according to one aspect of the presentdisclosure;

FIG. 4 is a circuit diagram showing a device threshold resisteradjustment, according to one aspect of the present disclosure;

FIG. 5 is a circuit block diagram showing error correction, according toone aspect of the present disclosure;

FIG. 6 is a block diagram of a system under manufacturing fabrication,testing and optionally programming, according to one aspect of thepresent disclosure;

FIG. 7 shows a flow diagram illustrating device selection fromfabricated distribution, according to the various aspects as describedherein;

FIG. 8a shows a flow diagram illustrating device selection andprogramming, according to the various aspects as described herein;

FIG. 8b shows a continuation flow diagram of FIG. 8a illustrating deviceselection and programming, according to the various aspects as describedherein;

FIG. 9 shows a flow diagram illustrating temperature compensation,according to the various aspects as described herein;

FIG. 10 is a flow diagram illustrating temperature compensation factorcalculation, according to one aspect of the present disclosure.

DETAILED DESCRIPTION

The following detailed description describes the present aspects withreference to the drawings. In the drawings, reference numbers labelelements of the present aspects. These reference numbers are reproducedbelow in connection with the discussion of the corresponding drawingfeatures.

As a preliminary note, any of the aspects described with reference tothe figures may be implemented using software, firmware, hardware (e.g.,fixed logic circuitry), manual processing, or a combination of theseimplementations. The terms “logic,” “module,” “component,” “system” and“functionality,” as used herein, generally represent software, firmware,hardware, or a combination of these elements. For instance, in the caseof a software implementation, the terms “logic,” “module,” “component,”“system,” and “functionality” represent program code that performsspecified tasks when executed on a processing device or devices (e.g.,CPU or CPUs). The program code can be stored in one or morenon-transitory, computer readable memory devices.

More generally, the illustrated separation of logic, modules,components, systems, and functionality into distinct units may reflectan actual physical grouping and allocation of software, firmware, and/orhardware, or can correspond to a conceptual allocation of differenttasks performed by a single software program, firmware program, and/orhardware unit. The illustrated logic, modules, components, systems, andfunctionality may be located at a single site (e.g., as implemented by aprocessing device), or may be distributed over a plurality of locations.

In one aspect, an inverter-based analog to digital converter (ADC) isprovided that uses a digital inverter circuit as a comparator. Theinverter includes NMOS (n-Type Metal Oxide Semiconductor) and PMOS(p-Type Metal Oxide Semiconductor) device active at the same timeproviding a direct current path between a power rail and ground. Acrowbar current is a large contributor to the total power consumption ofconventional inverter based ADCs as many of the inverters will have bothdevices active for some period of time. In one aspect, the designdescribed below in detail avoids this wasted power by the use of adynamic discrete time architecture where an input signal is onlyconnected to a gate of the NMOS devices after an output pre-chargecycle. Using a pre-charge circuit provides significant power reduction,as described below in detail.

In one aspect, an inverter based multi bit flash comparator is used toperform analog to digital conversion. A sample and hold circuit performsa programmable DC (direct current) level shift followed by a series ofdynamic digital inverters; where enhancement mode NMOS devices havedifferent gate voltage thresholds. The series of inverters produce ascrambled thermometer encoded output. As an example, more than 2^(n)inverters are used to provide increased manufacturing yield. The multibit flash comparators may be time interleaved to increase conversionperformance. The number of flash comparators that are time interleavedis determined by flash comparator performance and system performanceneeds.

In one aspect, the flash comparator scrambled thermometer output isprovided as an input into a device selection block. The device selectionblock uses an optional temperature and voltage compensation logic andconfiguration information programmed during manufacturing testing,calibration and characterization to select and order the scrambleddevice outputs from the flash comparator to an ordered thermometerencoded output. During semiconductor wafer probe, the temperature andvoltage are swept and changes to the configuration data are saved tomodify comparator selection as the temperature and voltage varythroughout the operation of the system. The selection changes can bemade seamlessly during a circuit pre-charge phase. As an example, thenumber of inputs into the device selection block may be greater than thenumber of outputs to improve product yield.

Furthermore, the ordered thermometer encoded output from the deviceselection block is input into an optional error detection and correctionblock, as described below. The error detection and correction block maybe implemented by detecting multiple transitions within the thermometerencoded value to detect errors or use past values and/or extra redundantdevices to limit the amount of worst case conversion error. The variousaspects are not limited to any specific implementation.

In another aspect, a state machine is also provided that uses amultiplexer to consolidate/converge outputs from the time interleavedpaths mentioned above, to produce a single output. The point forperforming the convergence is chosen to allow individual flashcomparators, device selections and error corrections logic whileenabling sharing of the thermometer to one-hot encoding and the one-hotencoding to binary encoding logic. The amount of interleaving may beadjusted along with changes in the allowed conversion time to compensatefor temperature and voltage variations. These parameters may bedetermined during manufacturing, test and stored at an on-chip,non-volatile memory.

In one aspect, a thermometer to one-hot encoding block is provided thatexamines the thermometer encoded value for a transition from an activeto inactive state. This transition is likely to occur once in an errorfree thermometer encoded value. The output represents the position ofthe transition with only one active output signal. The one-hot encodedvalue is then encoded into a final binary output value.

In one aspect, the flash comparator design of the present disclosureuses NMOS devices with a spread of voltage thresholds. The NMOS gatevoltage threshold spread may be accomplished using charge tunneling,body effect offset, source resistance, device sorting or otherwise.

Charge tunneling is based on Fowler-Nordheim tunneling or hot electroninjection methods depending on circuit design and device layout. Incharge tunneling, a tunneled charge causes a floating-gate transistor toact like an electron gun. The excited electrons are pushed through andtrapped on another side of a thin oxide layer, giving it a negativecharge. The negatively charged electrons act as a barrier between acontrol gate and a floating gate. As charge is trapped in the gateoxide, the amount of gate voltage to activate a NMOS device channel isincreased. The initial un-programmed device thresholds could be adjustedthrough process parameters to a very low threshold. The charge tunnelingapproach would have the advantage of a small size and low power as theamount of redundancy could be minimized reducing the total number ofdevices that are switching. The process may use a fabrication technologyprocess used in a Flash memory process and not conventional digitalprocess. In another aspect, a conventional digital or analog fabricationtechnology process is used for fabrication.

One of the side effects of deep submicron processes is the increasedstandard deviation in device gate voltage thresholds, which isundesirable for a conventional analog design. The ADC circuit of thisdisclosure exploits this normally undesirable attribute, which increasesthe statistical device threshold distribution.

Conventional analog layout techniques are normally deployed to attemptto more closely match MOS (metal-oxide semi-conductor) devices. In thepresent design described below, an increase in the standard deviationmay be desirable to achieve the desired results.

A device sorting approach provides a design compatible with conventionaldeep submicron digital or analog processes. On the other hand therewould be more redundant devices used to increase manufacturing yieldleading to increased power consumption of a charge injection basedthreshold adjustment.

As the devices size decreases the standard deviation of the gate voltagethreshold increases. In other words, process shrinks only improves theproposed design which is contrary to most other analog circuits.

In one aspect, additional redundant devices would be added to the designdescribed below and during wafer probe testing, the devices with theclosest threshold to a desired value are selected for each quantizationstep. The device selection and ordering would then be programed into amemory. If devices could not be selected for each quantization step, thedie is marked as defective and discarded. This provided a balancebetween the added redundant devices and manufacturing yields.

In one aspect, the manufacturing yield benefits from error correctionschemes that are implemented. There is an opportunity to examinethermometer bit encoding from a flash comparator before it is convertedinto one-hot encoding to provide error detection and correctioninformation.

In one aspect, the system architecture described below using a digitalinverter gate threshold quantization may compress an input signal range.A DC offset is added to the held analog input and the disclosed designprovides scaling to compensate for input signal compression.

In one aspect, the manufacturing cost of a system is reduced byemploying the adaptive design of this disclosure on a communicationslink, some of the tester characterization can be avoided and linktraining may be used to select an order of the inverter based flashcomparators.

In one aspect, the disclosed system selects or programs more devicesabove and below a desired input voltage range to allow device selectionto compensate for temperature or core voltage changes that occur afteran initial device selection or programming process. In another aspect,the same techniques used for temperature and core voltage compensationmay be used to extend a yield of devices that have failed the sortingprocess. It is noteworthy and without limitation, the term core voltageused throughout this specification means the voltage that is provided topower circuits in a system. Furthermore, the term temperature or systemtemperature is intended to mean the die temperature, i.e. thetemperature that circuit elements of a system are subjected to duringoperation.

In one aspect, conversion time(s) may be decreased to compensate forincreased temperature or increased to compensate for decreasedtemperature or vice versa depending on if the device threshold isinversely proportional or proportional to temperature respectively. Inone aspect, the conversion time(s) may be decreased to compensate forincreased core voltage or increased to compensate for decreased corevoltage or vice versa, depending on if the device threshold is inverselyproportional or proportional to core voltage, respectively. In yetanother aspect, different conversion times may be used for differentconversion bit ranges or a separate conversion time for each invertercompare function.

In one aspect, conventional analog design and layout practices fordevice matching are purposely violated to provide a wider devicethreshold distribution. The conventional analog design rules for devicematching include device orientation, guard ring isolation, proximity toother devices or structures, build large components out of manyidentical units, use of stacked layout for large devices, use ofcommon-centroid symmetry, consider boundary conditions, use of dummydevices if necessary, minimize parasitic series resistance by using asmany contacts as possible, use stacked structures to realize largetransistors to minimize diffusion capacitance, use multiple fingers tominimize gate resistance to minimize noise and maximize speed, maximizespacing between critical analog and digital components, minimizeconnection to critical nodes, minimize coupling or crossing betweensensitive lines, use shields whenever space and speed allow and otherwell-known design and layout techniques.

In one aspect, the selection of a new set of devices may be selected upor down a device threshold curve.

In one aspect, the system of the present disclosure provides a digitaloffset value to be added or subtracted from an unadjusted digital outputvalue to compensate for temperature and voltage changes that occurduring system operation. These offset values may be stored in a memorythat is addressed by the measured device temperature and core voltage.

In one aspect, a diode drop or fraction of a diode drop voltage is addedto a sampled analog voltage during a sample and hold process. In anotheraspect, a programmable digital offset voltage value is added to thesampled analog voltage during the sample and hold process.

In one aspect, scaling of a sample and hold circuit is adjusted toprovide a non-unity gain to adjust for temperature, core voltage or toincrease manufacturing yield.

In one aspect, adjustments may be made to a device body voltage toadjust a device threshold voltage curve up or down to compensate forchanges in temperature, core voltage or to increase manufacturing yield.Increases in body voltage cause an increase in voltage threshold forNMOS devices and vice versa. Decrease in body voltage cause an increasein voltage threshold for PMOS devices and vice versa.

In one aspect, source devices may be enabled or disabled to adjust aresister to move the device threshold curve up or down as needed. Inanother aspect, different values of source resistors selected to providea wider range of device thresholds.

In one aspect, optimum device programming, characterization,compensation temperature and core voltage are selected to be differentfrom the ambient temperature and nominal voltage to provide the besttemperature and core voltage compensation.

In one aspect, source devices may be enabled or disabled to adjust thesource resister to move the device threshold curve up or down as needed.In another aspect, a memory includes information used to modify thedigital output 108 to compensate for changes in temperature and voltage.

System 100: With the foregoing in mind, systems and methods of thepresent disclosure will be described in more detail with respect toexample aspects shown in the figures. It is understood that variousother aspects of the disclosure are also disclosed and described hereinand more fully describe the scope of the disclosure in various aspects.

In one aspect, FIG. 1 shows a system 100 that provides a timeinterleaved flash ADC without temperature compensation using flash ADCmodules 104A-104N (may be referred to as flash ADC 104 or flash ADCs104). The number of ADC modules 104A-104N may vary from system to systemfrom 1 to any number.

In system 100, a continuous analog input 102 is converted to a discretedigital representation. The analog input 102 could represent a voltage,current, radiation level or any other continuous value input. Each flashADC modules 104A-104N provides a partial digital output to a mergemodule 106 that is controlled by an interleave control module 110. Theoutput from merge module 106 is the discrete digital output 108. Sincethe time used by a single flash ADC may be too long to perform theconversion to meet system needs, multiple flash ADCs 104A-104N are timeinterleaved to provide an aggregate increase in conversion rateperformance, as described below in detail.

System 200A: In one aspect, FIG. 2a is a block diagram of a system 200Athat provides a time interleaved inverter based ADC, without temperatureor core voltage compensation, according to one aspect of the presentdisclosure. System 200A includes a plurality of inverter based, flashcomparator modules (may also be referred to as flash compare modules)202A-202N that sample the analog input 102 and provide unordered outputsignals 204A-204N corresponding to each, inverter based flashcomparators. In one aspect, the comparators within the flash comparatormodule 202A-202N are composed of a circuit based on a digital invertergate. The number of flash comparator modules 202A-202N may vary fromsystem to system from 1 to any other number and the various aspectsdisclosed herein are not intended to limit the number of timeinterleaved flash comparator modules to any specific number. Details ofa flash comparator module 202A-202N are described below as CircuitDiagram 300A and Circuit Diagram 300B in FIG. 3a and FIG. 3b ,respectively.

The unordered flash comparator module 202A-202N outputs the set ofunordered output signals 204A-204N that represent outputs from eachcomparator. The number of unordered output signals 204A-204N will dependon the number of comparators within each flash comparator module202A-202N. The number of comparators may depend on integrated circuitmanufacturing transistor threshold distribution, number of bits ofdigital resolution, adjustability of transistor thresholds, circuitmanufacturing yield goals, an amount and type of temperaturecompensation, a conversion rate and other factors. The various aspectsdescribed herein are not limited to any specific factor.

The set of unordered output signals 204A-204N are input into a deviceselection module 206A-206N. The device selection modules 206A-206N orderthe unordered output signals 204A-204N into uncorrected thermometerencoded signals 208A-208N. In one aspect, the device selection module206A-206N may be composed of a set of multiplexers with output selectioncontrols provided by configuration data 216A-216N from configurationdata module 214A-214N. In one aspect, the process used to obtaining theselection configuration data, conversion time, DC offset value and otherdata is described below in the flow diagram of FIG. 7.

In one aspect, the selection of the unordered signals 204A-204N to formthe uncorrected thermometer encoded signals 208A-208N may be implementedusing manufacturing testing and optional programming. In another aspect,the process of selection of the unordered signals 204A-204N to formuncorrected thermometer encoded signals 208A-208N may be implemented byon die circuits allowing dynamic run time device selection. In anotheraspect, signal connection and ordering is added during the manufacturingprocess after initial device characterization testing. Configurationdata 216A-216N from configuration data module 214A-214N may be used bythe device selection module 206A-206N to transform the unordered signals204A-204N into uncorrected thermometer encoded signals 208A-208N. In oneaspect, the configuration data 216A-216N is stored in volatile such asSRAM, DRAM, Latches, Flip/Flops, logic gates or other memory types. Inanother aspect, the configuration data is stored in nonvolatile memorysuch as ROM, EPROM, EEPROM, Flash, phase change, disk, tape or othermemory types. In yet another aspect, the configuration data is stored infuses that are programmed during manufacturing test process. The fusesmay be sampled upon power up or directly connected throughout the systemoperation. The various aspects described herein are not limited to anyspecific storage type.

The ordered uncorrected thermometer encoded signals 208A-208N representthe analog input 102. This set of signals may include redundant signalsor extra signals. The redundant signals or extra signals may representanalog input 102 values in between the normal quantization digitalsteps. The nominal number of signals within the unordered signals204A-204N and ordered uncorrected thermometer encoded signals 208A-208Nis given by 2^(n) where n is the number of bits in the digital output108. There are likely more unordered signals 204A-204N than ordereduncorrected thermometer encoded signals 208A-208N to providemanufacturing yield enhancements.

In one aspect, error correction modules 210A-210N accept the ordereduncorrected thermometer encoded signals 208A-208N and provides correctedthermometer encoded signals 212A-212N. The error correction modules210A-210N may use various techniques to correct the errors. In oneaspect, redundant signals are included in the thermometer encodedsignals 208A-208N where these redundant signals provide a representationof the analog input 102 value that is in between a desired quantizedvalue. In another aspect, redundant signals are included in thethermometer encoded signals 208A-208N where the redundant signalsprovide a representation of the analog input 102 value that is equal toother represented values. In yet another aspect, the thermometer encodedsignals 208A-208N are examined for anomalies in the thermometerencoding. An example of such anomalies would be a thermometer encodedsignal 208A-208N with a zero value followed by a higher ordered signalwith a one value such as the following 8-bit sequence “00101111”. Anexample circuit for error correction is described in more detail withrespect to system 500 of FIG. 5. The corrected signal set 212A-212Ncontains 2^(n) again where n is the number of bits in the digital output108.

The corrected signal set 212A-212N is provided to a Mux 222 that iscontrolled by a state machine 218 using multiplexer selection signals220. The state machine module 218 controls the sequencing to achieveanalog to digital convertor time interleaving. In one aspect, the statemachine module 218 processes are implemented using hardware sequencers.In another aspect, the state machine module 218 processes areimplemented using software instructions that are machine executable. Inyet another aspect, the state machine module 218 processes areimplemented using a combination of hardware sequencers and softwareinstructions. The state machine module 218 may provide controls, forexample, clock signals, reset signals, pre-charge signals, convertsignals, program address, program signal and other control signals. Thestate machine module 218 provides the multiplexer selection signals 220to time multiplex the sets of thermometer encoded corrected signals212A-212N.

The multiplexer 222 is used to time multiplex the different set ofthermometer encoded corrected signals 212A-212N. There is a set ofthermometer encoded corrected signals 212A-212N for each of the timeinterleaved ADC 104A-104N. The multiplexer 222 sequences through themultiple slower rate streams of thermometer encoded corrected signals212A-212N to form a time multiplexed interleaved thermometer encodedfull conversion rate signal 224 that represents a quantized version ofthe analog input 102.

Signals 224 are provided to a thermometer to one-hot encoding module 226that outputs converted one-hot encoded signals 228. In one aspect, thethermometer to one-hot encoding module 226 also provides errorcorrection functionality. One aspect of an example circuit of thethermometer to one-hot encoding module 226 is shown in FIG. 5.

The one-hot signals 228 are then provided to a binary encoding module230 that converts the signal into a binary encoding that represents thedigital output 108. The digital output 108 is a quantized digitalrepresentation of the analog input 102. The number of binary weightedsignals may be represented by log₂ of the number of one-hot encodedsignals 228.

System 200B: FIG. 2b shows a system 200 b that is a modified version ofsystem 200 a described above with respect to FIG. 2a , according to oneaspect of the present disclosure for temperature and core voltage devicethreshold compensation. System 200 b has components that may also beused in system 200 a and for brevity sake, those components are notdescribed again with respect to FIG. 2 b.

System 200 b provides a time interleaved flash ADC with device selectiontemperature and core voltage device threshold compensation. In oneaspect, system temperature and core voltage is measured and used tomodify device selection to compensate for device thresholds that maychange with temperature and core voltage. System 200 b includestemperature and voltage sensor module 234A-234N that measure systemtemperature and core voltage and output temperature and core voltagevalue signals 235A-235N that are provided to selection temperature andvoltage compensation module 232A-232N (also referred to as module232A-232N). The temperature and core voltage value signals 235A-235Nprovide a digital value representation of the system temperature andcore voltage. In one aspect, each of the time interleaved ADC has adedicated temperature and voltage sensor module 234A-234N. In anotheraspect, multiple time interleaved ADC share a temperature and voltagesensor module 234A-234N.

The selection temperature and voltage compensation module 232A-232N usesthe information provided by the temperature and core voltage valuesignals 235A-235N to modify configuration data 216A-216N to form thetemperature core voltage compensated configuration data 233A-233N. Inone aspect, the process of the selection temperature and voltagecompensation module 232A-232N is described in the flow of diagram ofFIG. 9. In one aspect, the process for obtaining the temperature,voltage and other compensation data is described below in the flowdiagram of FIG. 10. In one aspect, the system 600 used for obtaining thetemperature, voltage and other compensation data is described below withrespect to FIG. 6.

System 200C: FIG. 2c shows a system 200 c that is a modified version ofsystem 200 a described above with respect to FIG. 2a for temperature andcore voltage device threshold adjustment compensation, according to oneaspect of the present disclosure. System 200 c has components that mayalso be used in system 200 a and 200 b and for brevity sake, thosecomponents are not described again with respect to FIG. 2 c.

In system 200 c, the temperature and voltage threshold compensationmodule 236A-236N receives the system temperature and core voltage valuesignals 235A-235N from a temperature and voltage sensor module 234A-234Nand uses signals 238A-238N to modify the conversion device voltagethreshold of the sensing devices within the flash comparator module202A-202N. In one aspect, each of the time interleaved ADC has aseparate temperature and voltage sensor module 234A-234N. In anotheraspect, multiple time interleaved ADCs share a temperature and voltagesensor module 234A-234N.

In one aspect, the device voltage threshold is adjusted by changing thedevice body voltage. In another aspect, the device voltage threshold isadjusted by switching in different source resisters. A source resistoris a device connected between the conversion device source terminal andground potential for NMOS devices and a voltage potential for PMOSdevices. In yet another aspect, the device voltage threshold is adjustedby tunneling charge into or out of the device gate oxide. In one aspect,the process used to adjust the device threshold as described below inthe flow diagram of FIG. 8a and FIG. 8b . In another aspect, the devicevoltage threshold is adjusted by changing a source resistor value. Inone aspect, the source resistor value is changed by trapped charge. Inanother aspect, a MOS device is used as a source resistor. In anotheraspect, a source resistor MOS device is adjusted to compensate fortemperature and core voltage changes and increase manufacturing yield bychanging the gate voltage. In another aspect, the source resistor valueis changed by a resistor adjusting circuit 401 shown in FIG. 4 anddescribed below in detail. In one aspect, the temperature, voltage andother compensation data is obtained using the process flow of FIG. 10.In one aspect, the system 600 used for obtaining the temperature,voltage and other compensation data is described below with respect toFIG. 6.

System 200D: FIG. 2d shows system 200 d that provides yet anotherexample of a time interleaved flash ADC with digital temperature andcore voltage device threshold compensation, according to one aspect ofthe present disclosure. System 200 d has components that may also beused in system 200 a and 200 b and for brevity sake, those componentsare not described again with respect to FIG. 2 d.

System 200 d includes a digital temperature and voltage compensationmodule 240 that modifies uncompensated digital signals 239 to form thedigital output 108. The temperature and voltage sensor module 234measures the die temperature and core voltage and provides temperatureand core voltage information 235 to the digital temperature and voltagecompensation module 240. In one aspect, the digital temperaturecompensation is performed by adding or subtracting compensation datafrom the uncompensated digital signals 239. In one aspect, the digitaloutput 108 is modified for error correction. In one aspect, thetemperature, voltage and other compensation data is obtained using theprocess of FIG. 10. In one aspect, the system 600 used for obtaining thetemperature, voltage and other compensation data is described below withrespect to FIG. 6. As an example, the compensation data may be stored inSRAM, ROM, EPROM, EEPROM, Flash, Latches, Flip/Flops, Disk, DRAM, PhaseChange Memory, Tape or any other storage medium.

System 200E: FIG. 2e shows system 200 e, yet another example, of a timeinterleaved flash ADC with conversion time temperature and core voltagedevice threshold compensation, according to one aspect of the presentdisclosure. System 200 e has components that may also be used in system200 a and 200 b and for brevity sake, those components are not describedagain with respect to FIG. 2 e.

In system 200 e, the temperature and voltage sensor module 234 measuresthe die temperature and core voltage and provides temperature and corevoltage information 235 to the state machine module 218. Thistemperature and core voltage information 235 may also be provided to theflash compare module 202A-202N. In one aspect, each comparator withinthe flash compare module 202A-202N uses an independent conversion timebased on device parameters and temperature and core voltage compensationinformation 235. Due to the different conversion times, the unorderedsignal set 204A-204N may be held by the flash comparator module202A-202N or another module if there is a significant difference betweena fastest and slowest conversion time after considering temperaturecompensation conversion time adjustments. In one aspect, the number ofADCs 104A-104N time interleaved is adjusted to match the slowesttemperature adjusted conversion times of the comparators within theflash comparator module 202A-202N with expected system performance. Inone aspect, the conversion time is adjusted to match device processparameters to a desired analog to digital conversion transfer function.In one aspect, the conversion time is adjusted to match the desired DCoffset while providing the desired analog to digital conversion transferfunction.

Circuit 300A: FIG. 3a shows a circuit diagram 300 a for a flashcomparator module 202A-202N depicting un-programmable device thresholdselection using inverter based comparators 310A-310N, in one aspect ofthe present disclosure. A dynamic circuit architecture is depicted forillustrative purposes and is not intended to limit the disclosure to anyone type of inverter architecture. The adaptive aspects described hereinare not limited to any specific number of inverter based comparators310A-310N. The number of inverter based comparators 310A-310N may varyfrom system to system from 1 to any other number. The number of inverterbased comparators 310A-310N in a system depends on the number of bits ofresolution desired in the digital output 108, the device thresholddistribution of the fabrication process, the adjustability of the devicethreshold, the system operating temperature range, the system corevoltage operating range, the analog input 102 voltage swing, the amountof and the method of used error correction, the system die size target,the system cost target, the manufacturing system yield target and otherfactors. In one aspect, the inverter based comparators 310A-310N arerealized using a complementary architecture where the NMOS and PMOSgates are controlled by the same or similar signal. In another aspect,the inverter based comparators 310A-310N are realized using a dynamicarchitecture where the NMOS and PMOS gates are not controlled by thesame or similar signal.

A pre-charge signal 302 via inverter 303 starts a conversion cycle bypre-charging an internal node 315A-315N of each of the inverter basedcomparators 310A-310N, for example, to a logic “1” value throughpre-charge devices 312A-312N. The internal node 315A-315N value isinverted by digital inverters 316A-316N to provide a logic “0” value onthe unordered thermometer encoded output 204 for all inverter basedcomparators. Pre-charge signal 302 is deactivated followed by theactivation of a convert signal 304. The convert signal 304 enables theanalog input 102 captured by the sample and hold circuit 306 to pass tothe gate inputs of conversion devices 314A-314N through pass gate switch308. In one aspect, the function provided by an optional pass gateswitch device 308 is included within the sample and hold module 306.

In one aspect, the convert signal 304 is optionally used to start adelay line signal pulse through inverter pairs 320A-320M. This aspect isnot intended to limit the number of inverter pairs 320A-320M to anyspecific number. The number of inverter pairs 320A-320M may vary fromsystem to system from 1 to any number. The number of inverter pairs320A-320M in the system will depend on the minimum and maximumcomparator processing time over a desired system operating temperatureand core voltage range. In one aspect, the inverter pairs 320A-320M maybe used to provide compensation for temperature and core voltagevariations as the system temperature and core voltage varies. Theconversion time selection module 326 receives temperature and corevoltage data 235 from temperature and voltage sensor module 234 and usesthis temperature and core voltage data 235 to adjust the selectionsignals 328 to adjust the corresponding delay between the convert signal304 and a sample signal 325. This delay is the conversion time of theADC. In one aspect, the delay between the convert signal 304 and thesample signal 325 is provided by a series sequence of digital logicgates, counter, shift register, wire delay, digital circuit,microprocessor, state machine, capacitive circuit, resistive circuit orother circuit mechanism.

In another aspect, conversion time function as defined is the time delaybetween the assertion of the convert signal 304 and the assertion of thesample signal 325 is provided as part of the time interleaving process.In yet another aspect, the conversion time may vary between the analogto digital converters that are time interleaved. The time intervals ofthe time interleaving may be compressed or stretched to match the deviceselection and to compensate for device temperature and core voltagevariations. The digital values could be latched to smooth the timeinterval changes from the digital output 108.

In one aspect, circuits and devices are designed to provide offsettingtemperature and core voltage variation cancellation as the threshold ofthe conversion device 314A-314N decreases circuit components includingpossibly the conversion devices 314A-314N slow down to cancel theseeffects and vice versa. At the end of the delay line propagationinverter pair 324 is used to drive gating devices 318A-318N that connectthe outputs from inverters 316A-316N to the set of unordered thermometerencoded output signals 204. In another aspect, the inverter pair 324 isoptional and the sample gate devices 318A-318N are driven directly by amultiplexer 322. In yet another aspect, the outputs for the inverters316A-316N directly provide the set of unordered for thermometer encodedoutput signals 204. The conversion time selection module 326 adjust theamount of time delay between the activation of the convert signal 304and the sampling of the inverter based comparators 310A-310N throughinverters 316A-316N and gate devices 318A-318N.

The output signal 328 from the conversion time selection module 326provides the selection input for multiplexer 322. The multiplexer 322selects different signal paths that contain varying number of inverterpairs 320A-320M each inverter pair 320A-320M adding a small amount ofsignal delay leading to variation in the total signal propagation delay.The amount of signal delay is selected to match a desired processingtime of the inverter based comparators 310A-310N. The sample and holdcircuit 306 samples the analog input 102 and holds the sampled analogvalue through the desired conversion time. In one aspect, the sample andhold circuit 306 performs load amplification to drive the addedcapacitance of the gate inputs of conversion devices 314A-314N. In oneaspect, the sample and hold module 306 may include a direct current (DC)voltage offset to move the sampled analog input 102 within the thresholdvoltage range of the conversion devices 314A-314N. In one aspect, the DCvoltage offset is programmable and may use a different value for eachflash comparator module 202A-202N. In another aspect, gain scaling isused to compensate for the input voltage compression that may be causedby adding the DC offset voltage. The conversion devices 314A-314N willbe operating in one of three regions of operation including cutoff,linear or saturation depending on the device fabrication parameters andthe analog input 102 value.

Circuit diagram 300A depicts the use of metal oxide semiconductorfield-effect transistor (MOSFET) devices for illustrative purposes andis not intended to limit the devices used to any type of device, devicetechnology or manufacturing process technology.

Circuit 300B: FIG. 3b shows a circuit diagram 300 b of flash comparemodule 202A-202N depicting conversion devices with programmable devicethresholds. Circuit 300 b includes various components that are also usedin circuit 300 a and for brevity are not described again.

Circuit 300 b includes a plurality of programmable conversion devices330A-330N similar to conversion devices 314A-314N of FIG. 3a , exceptfor devices 330A-330N, the device threshold is adjustable for example,by using charge tunneling techniques. In another aspect, the thresholdof the programmable conversion device 330A-330N is adjustable by changesto a device body bias value. In yet another aspect, the threshold of theprogrammable conversion device is 330A-330N is adjusted by changes to asource resistance as described below with respect to FIG. 4.

In FIG. 3b , a program address signal 332 is decoded by a decoder module342 to select one of the programmable conversion devices 330A-330N forthreshold adjustment. A program signal 334 controls the conversiondevice 330A-330N threshold adjustment operation when asserted. Anoptional inverter 335 inverts the active level of the program signal 334when it is input into a gate input of the PMOS programming voltagedevice 336. The programming voltage device 336 is used to reply aprogram in voltage 338 to a gate terminal of the programmable conversiondevice 330A-330N. A plurality of NAND gates 340A-340N are used to drivethe pre-charge devices 312A-312N and the drain pull-down device313A-313N.

During threshold adjustment, the decoder module 342 uses program addresssignals 332 and the program signal 334 to select which output signals344A-344N to drive to a logical “1” or logical “0” value. The pre-chargesignal 302 is held active (logical “1”) during threshold adjustment.When the decoder module 342 is performing threshold adjustment, outputsignal 344A-344N are asserted to a logical “0” for the inverter basedcomparators 310A-310N that include the selected programmable conversiondevices 330A-330N. The NAND gate 340A-340N that corresponds to theselected programmable conversion device 330A-330N provides an activehigh signal to pre-charge device 312A-312N and drain pulldown device315A-315N. The corresponding pre-charge device 312A-312N is forcedinactive and the corresponding drain pulldown device 313A-313N is forcedactive bringing the corresponding internal node 315A-315N to the groundpotential. This large voltage difference between the selected gatevoltage and the drain terminal that is connected to the internal node315A-315N causes a tunneling current to flow allowing charge to betrapped in the device oxide or floating gate. The process is reversed toremove charge from a device.

The non-selected inverter based comparators 310A-310N have theircorresponding pre-charge devices 312A-312N active and their drainpull-down devices 313A-313N inactive resulting in a correspondinginternal node 315A-315N voltage that prevents the flow of a significantamount of tunneling current allowing the threshold of the correspondingprogrammable conversion device 330A-330N to remain virtually unchanged.Adding negative charge (electrons) into the gate oxide increases theprogrammable conversion device 330A-330N threshold. There is analogousprocess for removing charge to adjust the threshold of the programmableconversion device 330A-330N. Removing charge (remove electrons) from thegate oxide or floating gate decreases the programmable conversion device330A-330N threshold.

Circuit diagram 300B depicts the use of charge tunneling to adjust thethreshold of the programmable conversion devices 330A-330N forillustrative purposes and is not intended to limit the method used toadjust the device threshold. Furthermore, circuit diagram 300B depictsthe use of metal oxide semiconductor field-effect transistor (MOSFET)devices for illustrative purposes and is not intended to limit thedevices used to any type of device, device technology or manufacturingprocess technology.

System 400: FIG. 4 shows a system 400 using an adjustable sourceresister to modify a conversion device 402 threshold. An adjustmentcircuit 401 is shown separately from the NMOS conversion device 402whose threshold is modified. In one aspect, the NMOS conversion device402 is a four terminal device with a gate terminal 404, a drain terminal406, a source terminal 408 and a body terminal 410. The body terminal410 is also referred to as the substrate terminal. Typically the bodyterminal 410 is connected to ground (VSS) for NMOS devices and VDD forPMOS devices. The device threshold of the NMOS conversion device 402changes with varying voltage difference between the source terminal 408and the body terminal 410. As the voltage between the source terminal408 and the body terminal 410 is increased the gate voltage threshold ofa NMOS conversion device 402 increases. The opposite is true for a PMOSdevice; an increase in the source terminal 408 to body terminal 410voltage results in a decrease in the device gate threshold voltage.

The NMOS conversion device 402 has an adjustable resistor 412 connectedbetween its source terminal 408 and ground (VSS). As charge currentpasses through the NMOS conversion device 402 from drain terminal 406 tothe source terminal 408, it also passes through the adjustable resister412 before reaching the circuit ground (VSS). As charge current passesthrough the adjustable resister 412 a voltage is generated across theadjustable resister 412 that is proportional to the resistance. Thisgenerated voltage raises the voltage of the source terminal 408 to bodyterminal 410 voltage resulting in an increased threshold voltage for theNMOS conversion device 402. As the resistance of the adjustable resistor412 is increased so is the gate threshold voltage of the NMOS conversiondevice 402 and vice versa.

In one aspect, the adjustable resistor 412 is a MOS resistor consistingof a diffusion area covered by an insulator and a conducting layer abovethe insulator. The conducting layer is defined as adjusting terminal414. Optional resistors 426 and 428 form a voltage divider of thevoltage provided to the adjusting terminal 414, which is a function ofthe ratio of resistors 426 and 428 and the voltage on voltage node 424.In one aspect, resistors 426 and 428 are optional and voltage node 424is connected directly to adjusting terminal 414.

Different voltage values for voltage node 424 are achieved by activatingdifferent voltage sources 416A-416N. Each voltage source may beconnected to a different voltage supply value. The voltage source416A-416N is composed of a corresponding control signal 418A-418N, avoltage supply 420A-420N and a gate device 422A-422N. During operation,one of the control signals within the voltage source 416A-416N isasserted effectively connecting the corresponding voltage supply420A-420N to voltage node 424 bringing the voltage node 424 equal to thecorresponding voltage supply for 420A-420N. In one aspect, the voltagesources 4126A-416N are shared by multiple voltage nodes 424 associatedwith different NMOS conversion devices 402.

As the voltage is changed on the adjusting terminal 414, conductingcharges are increased or decreased in the diffusion and channel areas,if present, depending on the voltage applied to the adjustment terminal414. In one aspect, multiple device channels are constructed below theinsulating layer of the adjustable resistor 412 and within the diffusionlayer of the adjustable resistor 412. These channels form areas ofincreased resistance that change resistance with the application ofdifferent voltages to the adjustment terminal 414.

In one aspect, the resistance of the adjustable resistor 412 is modifiedby the use of charge tunneling process in to an oxide to provide anon-volatile adjustment. During the charge tunneling process electricalcharge is tunneled into or out of the insulating layer over thediffusion and channel areas of the adjustable resistor 412. In oneaspect, the adjustable resistor 412 is a depletion mode MOSFET.

In another aspect, the adjustment circuit 401 is replaced by a group ofdifferent valued resistors and switches to connect different resistancevalues between source terminal 408 and ground (VSS). In another aspect,a phase change element is used to provide the adjustable source resistorto adjust the conversion device threshold. In yet another aspect, amagneto-resistive element is used to provide the adjustable sourceresistor to adjust the conversion device threshold.

Circuit diagram 400 depicts the use of N-type metal oxide semiconductorfield-effect transistor (MOSFET) devices for illustrative purposes andis not intended to limit the disclosure to any type of device, devicetechnology or manufacturing process technology.

System 500: FIG. 5 shows a system 500 for an error correction circuitthat may be adaptively used in the error correction module 210A-210N,according to one aspect of the present disclosure. This circuit ofsystem 500 is a middle segment of a larger circuit. The middle segmentis used for illustrative purposes and is not intended to limit the sizeof the data being corrected.

In one aspect, system 500 includes a conversion section 502 thatreceives un-corrected thermometer encoded data 506D-506J (similar to theordered signal set 208A-208N described above) provides it to AND gates508D-508I. The most significant input of AND gates 508D-508I isinverted. For example, the inputs into AND gate 508D is a positive copyof signal 506D and an inverted copy of signal 506E. The output from ANDgate 508D-508I is uncorrected one-hot encoded data 510D-510I. Theone-hot encoded data 510D-510I may contain errors. An example of anerror would be is more than one of the one-hot encoded signals 510D-510Icontained a positive value (logic ‘1’).

Each output of one-hot encoded data 510D-510I is connected to fiveAND-OR gates 524D-524I except at the start and end of the data sequence,where the unavailable inputs would be set inactive as they are inputinto the AND-OR gates. A signal 514 is driven by an AND gate similar toAND gates 508D-508I, but represents an uncorrected one-hot encoded databit with one less bit of significance than signal 510D. As an example,signal 516 is driven by an AND gate similar to AND gates 508D-508I, butrepresents an uncorrected one-hot encoded data bit with two less bits ofsignificance than signal 510D. Signal 518 is driven by an AND gatesimilar to AND gates 508D-508I, but represents an uncorrected one-hotencoded data bit with one more bit of significance than signal 510I.Signal 520 is driven by an AND gate similar to AND gates 508D-508I, butrepresents an uncorrected one-hot encoded data bit with two more bits ofsignificance than signal 510I.

In one aspect, the AND-OR gate 524D-524I detects an error condition andcorrects it. For example if uncorrected one-hot encoded data 510D-510Iis represented by the binary value “010100” the corrected one-hotencoded data 526D-526I would be represented by the binary value“000100”. In another aspect, the error correction circuit 504 produces acorrected one-hot encoded data 526D-526I represented by the binary value“010000”. The use of any particular logic gate is for illustrativepurposes and is not intended to limit the use of any logic gate type.

System Block Diagram 600: FIG. 6 shows a block diagram of amanufacturing test and programming system 600, used according to oneaspect of the present disclosure. System 600 may be used to evaluate,test, characterize calibration and optionally program an ADC of thepresent disclosure. System 600 is not intended to limit the disclosureand actual system components may vary.

FIG. 6 shows a system under test 601, which is a system that isevaluated, tested, characterized and may be programmed with calibrationand configuration data, in one aspect of the present disclosure. Adevice programming control module 602 controls the overall evaluation,testing, characterization, calibration and any programming of the systemunder test 601. In one aspect, the system under test 601 is the ADC 100.In another aspect, the system under test 601 is a digital to analogconverter (DAC). In yet another aspect, the system under test 601 isanother type of analog, digital or mixed signal circuit system.

The device programming control module 602 generates control signals 604to control and optionally program the system under test 601. Statussignals 605 provide feedback from the system under test 601 to thedevice programming controller module 602, where the status signals 605may include temperature and voltage sensor data, interim data from thecircuit, timing information, testing status, calibration status,characterization data, programming status or other useful information.

In one aspect, analog voltage control signals 606 are used by the deviceprogramming controller module 602 to control and configure theprogrammable analog voltage control module 610. Analog voltage statussignals 607 provide feedback data and status from the programmableanalog voltage control module 610 to the device programming controllermodule 602. The analog voltage control module 610 provides the analoginput 102 to the system under test 601 during the testing, calibration,characterization or other procedures.

Output capture control signals 612 provide control for a digital outputcapture module 614 from the device programming controller module 602.Output capture status signals 613 provide status and the captureddigital output from the digital output capture module 614 back to thedevice programming controller module 602. The digital output capturemodule 614 is used to capture and report the digital output 108 from thesystem under test 601. The system under test 601 may be operating at asignificantly higher clock frequency than the device programmingcontroller module 602 so a programmed analog input 102 sequences anddigital output 108 capture sequences may be used.

Device control signals 616 are used to start, stop and control theoperation of the tester system operation. Device status signals 617provide status related to the system under test 601 and the testersystem operation. For example, a test running, testing passed or testingfailed status may be provided.

Environmental control signals 618 provide control information to anenvironmental temperature and voltage control module 620 from the deviceprogramming controller module 602. Environmental status signal 619provide status and state information to the device programmingcontroller module 602 from the environmental temperature and voltagecontrol module 620. The environmental temperature and voltage controlmodule 620 provides control over the tester system environmentalparameters applied to the system under test 601. These environmentalparameters may include temperature, direct current core voltage, directcurrent input and output driver voltage and other environmentalparameters.

Heating control signals 622 provides control information from theenvironmental temperature and voltage control module 620 to a heatingdevice module 624. The heating device module 624 is used to heat thesystem under test 601 above an ambient temperature. Cooling controlsignals 626 provide control information from the environmentaltemperature and voltage control module 620 to a cooling device module628 that is used to cool the system under test 601 below the ambienttemperature.

Direct current voltage control signals 630 provide control informationfrom the environmental temperature and voltage control module 620 to adirect current voltage control module 632 that provides a core and inputand output driver direct current voltage for the system under test 601.Direct current voltage signals 634 provide power from the direct currentvoltage control module 632 to the system under test 601.

It is noteworthy that the various aspects disclosed herein are notintended to limit the tester system 600 to only these modules. Thetester system 600 may have few or more modules depending on usedfunctions. It should be noted that multiple modules may be combined, butare shown separate for clarity purposes.

Flow Diagram 700: FIG. 7 shows a process 700 executed by the deviceprogramming controller module 602 or similar module for device selectionwith un-programmable devices, according to one aspect of the presentdisclosure. Process flow 700 is repeated for each flash comparatormodule 202A-202N. In one aspect, a separate process flow is executed inparallel for each flash comparator module 202A-202N.

The selection process flow 700 starts in block 702. The process proceedsto block 704 when the process determines if a reset is active. The resetforces the device programming controller module 602 or similar moduleprocessing the flow to the initial state as well as any flow relatedstorage, configuration data, other parts of the test andcharacterization system, the system under test 601 and any other areathat needs a specific initial state. If a reset is active in block 704,then the process simply waits in block 704 for the reset to becomeinactive.

If reset is inactive in block 704, then in block 706, a direct current(DC) offset voltage value is set to a certain value, for example, aminimum starting value. The analog input 102 is level shifted by the DCoffset voltage. This is executed to bring a sampled and held analoginput 102 within an active range of the conversion devices.

In block 708, the conversion time is set to a certain value, forexample, a minimum starting value. In block 710, a step count isinitialized to zero. The step count is a tracking number used by theprocess flow to represent the quantized digital output 108. The stepcount allows the process flow to associate flash comparator module202A-202N outputs to represent a digital output 108 value. In block 712,a list of active array elements of the flow process temporary storageare set to zero or another initial value. The active array elements holdthe association between the flash comparator module 202A-202N outputsand the step value which represents the digital output 108. The numberof active array elements is approximately equal to the number of flashcomparator module 202A-202N outputs.

In block 714, the analog input 102 is set to zero volts. In block 716,the nodes, for example 315A-315N, are pre-charged to a logical “1”value.

In block 718, the analog input 102 is sampled and held. In block 720,the held analog value is voltage shifted by the DC offset voltage. Inblock 722, the process waits for an amount of time equal to a currentconversion time. After the time delay, in block 724 the processdetermines if there are any new output valids (actives) from the flashcompare modules 202A-202N. In this case, new refers to the flash comparemodules 202A-202N outputs not already active during a previous iterationof the process flow.

If newly active outputs are detected, then in block 726 and the processstorage associated with the newly active outputs of the flash comparemodules 202A-202N are set to a value that represents a current 2^(n)step value. If no newly active outputs of the flash compare modules202A-202N are detected for the current conversion of the new analoginput 102 value, then in block 728, the process determines if this isthe first step value. If the current step value is the first value thenthe process proceeds to block 740 described below.

If the current step value is not the first value then no flash comparemodules 202A-202N outputs were detected to represent the digital valueof the analog input 102. This is considered to be an error andprocessing proceeds to block 730 to determine if adjustments could bemade and the system should be retested. It should be noted, that block728 is optional and needed when the digital output 108 value of zero isrepresented when no flash comparator module 202A-202N outputs areactive. If digital output 108 value of zero is represented by an activeflash comparator module 202A-202N output then block 728 would not bepresent.

In block 730, a current conversion time is compared to a maximum allowedconversion time. If the current conversion time is not equal, less than,the maximum conversion time, then in block 732 where the conversion timeis increased and the testing restarts at block 710. If the currentconversion time is equal to the maximum conversion time, then in block734 a test is performed on the current DC offset value. In block 734, ifthe current DC offset value is not equal, less than, the maximum DCoffset value then in block 736, the current DC offset value is increasedand the testing restarts at block 708. If the current DC offset value isequal to the maximum DC offset value system under test 601 is detectedas being bad then in block 738, an error flag is set indicating the testfailure after all available adjustments to conversion time and offsetvoltage have been made and unsuccessful processing completes in block752. For successful testing there is at least one new flash comparatormodule 202A-202 N output active for each tested analog input 102 valuefor a fixed conversion time and DC offset voltage value.

In another aspect, each flash comparator module 202A-202 N may haveunique values for conversion time and DC offset voltage as could beprovided by a more complex testing technique.

In block 726 and in block 728 when the current step is equal to zero,the first step, processing proceeds to block 740. In block 740, theprocess determines if the current step is the last step. There are 2^(n)steps starting at step equal to zero. In block 740, if the current stepis not equal to 2^(n)−1, last step, then in block 742, the current stepvalue is increased by one and then in block 744, the analog input 102 isset to the next test value and processing proceeds back to block 716 forcontinued testing of subsequent step values.

In block 740, if the current step is equal to 2^(n)−1, i.e. the laststep, the testing is completed. In block 745, the current system undertest 601 temperature and core voltage is sampled by the temperature andvoltage sensor module 234, 234A-234N. In block 746, the sampledtemperature and core voltage is stored in a memory device for use intemperature and core voltage compensation processing. In block 747, thesuccessful conversion time is stored in memory for operational use. Inblock 748, the successful value of the DC offset voltage is stored inmemory for operational use. In block 750, the associations between theflash comparator module 202A-202N outputs and the step values are storedin memory for operational use by device selection module 206A-206N foroperation and processing proceeds to a successful completion at block752. In process flow 700, the step value is described as an increasingvalue with each iteration of the process flow and is not intended tolimit the process flow and the process flow could be rewritten tosupport a decreasing step value.

Flow Diagram 800: FIGS. 8a-8b show a device selection process 800 forprogrammable threshold devices executed by the device programmingcontroller module 602 or similar module, according to one aspect of thepresent disclosure. Process 800 may be repeated for each flashcomparator module 202A-202N. In one aspect, a separate process flow isexecuted in parallel for each flash comparator module 202A-202N. Theselection process flow 800 starts in the start block 802.

In block 804, the process determines if a reset is active. If the resetis active in block 804, then the process waits in block 804 for thereset to become inactive. If reset is inactive then in block B806, adirect current (DC) offset voltage is set to a certain value, forexample, a maximum starting value. The analog input 102 is level shiftedby the DC offset voltage. This is performed to bring the sampled andheld analog input 102 within an active range of the conversion devices.

In block 808, the conversion time is set, for example, to a maximumstarting value. In block 810, the programmable devices are all erased bytunneling charge out of the oxide if needed. In block 812, the stepcount is initialized to 2^(n)−1. In block 814, the list of active arrayelements are set to zero or another initial value. In block 816, theanalog input 102 is set to a maximum value. In block 818, the variousnodes are precharged to a logical “1” value.

In block 820, the analog input 102 is sampled and held. In block 821,the held analog value is voltage shifted by the DC offset voltage. Inblock 822, the process waits for an amount of time equal to a currentconversion time. After the time delay, in block 824, a test is performedto determine if the number of inactive output valids from the flashcomparator modules 202A-202N is greater or equal to 2^(n). Thisdetermines if there are enough flash comparator modules 202A-202Noutputs that can be programmed to represent all of the digital output108 values from zero (0) to 2^(n)−1.

If the number of inactive output valids from the flash compare modules202A-202N is greater than or equal to 2^(n) then processing continues toblock 836 of FIG. 8b , where charge is tunneled. If the number ofinactive output valids from the flash compare modules 202A-202N is lessthan 2^(n), then the process determine if adjustments could be made andthe system retested. In block 826, the current conversion time iscompared to a minimum allowed conversion time. If the current conversiontime is not equal to the minimum conversion time, then in block 828, thecurrent conversion time is decreased and the testing restarts back atblock 810. If the current conversion time is equal to the minimumconversion time, then in block 830 the process determines if the currentDC offset value is equal to a minimum value. If not, then in block 832,the current DC offset value is decreased and the testing restarts backat block 808. If the current DC offset value is equal to the minimum DCoffset value, the system under test 601 is detected as being bad and anerror flag is set in block 834 indicating the test failure after allavailable adjustments to conversion time and offset voltage have beenmade and unsuccessful processing completes in block 872. For successfultesting, at least one new flash comparator module 202A-202 N outputactive is needed for each tested analog input 102 value for a fixedconversion time and DC offset voltage value.

In another aspect, each flash comparator module 202A-202N may haveunique values for conversion time and DC offset voltage as could beprovided by a more complex testing algorithm.

Referring now to FIG. 8b , in block 836, a programmable increment ofcharge is tunneled and captured in all devices where the outputs of theflash comparator module 202A-202N are inactive. In block 838, the analoginput 102 is set to the current value minus the voltage step value. Inblock 840, the nodes are pre-charged to a logical “1” value. In block842, the analog input 102 is sampled and held. In block 844, the heldanalog value is voltage shifted by the DC offset voltage. In block 846,the process waits for an amount of time equal to the current conversiontime. After the time delay, in block 848, the process determines ifthere are any new output valids that are inactive from the flashcomparator modules 202A-202N. In this case, new refers to the flashcomparator modules 202A-202N outputs not already inactive during aprevious iteration of the process flow.

If newly inactive outputs are detected, then in block 856, the storageassociated with the newly inactive outputs of the flash compare modules202A-202N are set to a value that represents the current step value. Ifno newly inactive outputs of the flash comparator modules 202A-202N aredetected for the current conversion of the new analog input 102 value,then in block 850, the process determines if the maximum amount ofcharge has already been tunneled during previous iterations. If themaximum amount of charge has already been tunneled into the devices,processing proceeds back to block 826, FIG. 8a , as described above. Ifthe maximum amount of charge has not already been tunneled into thedevices, then in block 852, a programmable increment of charge istunneled and captured in all devices where the outputs of the flashcomparator module 202A-202N are active and processing proceeds to backblock 840 for continued testing.

In block 856, process storage associated with the newly inactive outputsof the flash comparator modules 202A-202N are set to a value thatrepresents the current step value. In block 858, the process determinesif the current step is the last step. There are 2^(n) steps starting atstep equal to 2^(n)−1 and counting down to zero. In blocks 858, if thecurrent step is not equal to zero, i.e. the last step, then in block860, the current step value is decreased by one. In block 838, theanalog input 102 is set to the next test value and processing proceedsto block 840 for continued testing of subsequent step values.

In block 858, if the current step is equal to zero, i.e. the last step,the testing was successfully completed. In block 862, the current systemunder test 601 temperature and core voltage is sampled by thetemperature and voltage sensor module 234, 234A-234N. In block 864, thesampled temperature and core voltage is stored in a memory device foruse in temperature and core voltage compensation processing. In block866, the successful conversion time is stored in memory for operationaluse. In block 868, the successful value of the DC offset voltage isstored in memory for operational use and processing proceeds to block870. In block 870, the associations between the flash comparator module202A-202N outputs and the step values are stored in memory foroperational use by device selection module 206A-206N for operation andprocessing proceeds to a successful completion at block 872. In processflow 800, the step value is described as a decreasing value with eachiteration of the process flow and is not intended to limit the processflow and the process flow could be rewritten to support an increasingstep value.

Flow Diagram 900: FIG. 9 shows a process 900 for system temperature andcore voltage compensation processing executed by selection temperatureand voltage compensation module 232A-232N, Temperature and voltagethreshold compensation module 236A-236N, digital temperature and voltagecompensation module 240, state machine module 218 or similar moduleperforming compensation, according to one aspect of the presentdisclosure. The compensation process flow 900 starts in block 902.

In block 904, the process determines if a reset is active. If a reset isactive, then the process waits for the reset to become inactive. Ifreset is inactive in block 904, then in block 906, the currenttemperature and core voltage of the system is sampled. In block 908, thenewly sampled current system temperature and core voltage are stored ina memory for later processing.

In block 910, the device temperature and core voltage are sampled. Inblock 912, the sampled temperature is compared against an operatingrange. If the sample temperature is outside the system operating range,then in block 914, a flag is set signifying a temperature range errorand processing proceeds to block 930 where processing is completed.

If the sample temperature is within the system operating range, then inblock 916, the sampled core voltage is compared against the operatingrange. If the sample core voltage is outside the system operating range,then in block 918, a flag is set signifying a core voltage range errorand processing proceeds to block 930 where processing is completed.

If the sample core voltage is within the system operating range, then inblock 920, the delta temperature is calculated by subtracting the newlysample temperature from the saved temperature.

In block 922, the delta temperature is compared to a maximum range. Ifthe calculated delta temperature is greater than the maximum range, thenin block 924, a delta temperature error flag is set and processingproceeds to block 930 where processing is completed.

If the calculated delta temperature is less than the maximum range, thenin block 925, delta voltage is calculated by subtracting the newlysampled core voltage from the saved core voltage. In block 926, thecalculated delta core voltage is compared to a maximum range. If thedelta core voltage is greater than the maximum range, then in block 928,a delta core voltage range error flag is set and the process ends atblock 930.

If the delta voltage is not greater than the maximum range, then inblock 932, the process determines if either the delta temperature or thedelta core voltage are greater than a programmable threshold. If eitherthe delta temperature or the delta core voltage are greater than athreshold, processing proceeds to block 936. In block 936, the storedtemperature and core voltage compensation adjustment values areretrieved from a memory. In one aspect, the compensation adjustmentvalues retrieved are based on the current system temperature and corevoltage. In another aspect, the compensation adjustment values retrievedare based on the delta temperature and delta core voltage. In block 938,the retrieved temperature and core voltage compensation adjustmentvalues are used to adjust system parameters to compensate for thedigital output 108 differences for the same analog input 102 value dueto temperature and core voltage changes that are occurring during systemoperation. In block 940, the newly sampled system temperature and corevoltage are stored in a memory and processing proceeds to block 934.

If neither the delta temperature nor the delta core voltage are greaterthan a threshold processing as determined in block 932, then in block934, the processing is delayed for a programmable period of time toprovide stable system temperature and core voltage compensation. Thedelay provides hysteresis and control stability to the compensationprocess. After the expiration of the time delay in block 934, processingproceeds back to block 910. In one aspect, only temperature compensationis performed. In another aspect, only core voltage compensation isperformed.

Flow Diagram 1000: FIG. 10 shows a process 1000 for system temperatureand core voltage compensation factor data generation processing executedby device programming controller module 602 or similar module, accordingto one aspect of the present disclosure. The compensation datagenerating process 1000 starts in block 1002.

In block 1003, the process determines if a reset is active. If reset isactive in block 1003, the process waits for the reset to becomeinactive.

If reset is inactive in block 1003, then in block 1004 the system undertest 601 is configured into the operational state. In block 1005, acurrent temperature of the system under test 601 is set, for example, toa minimum operating temperature. In block 1006, the current core voltageof the system under test 601 is set, for example, to a minimum operatingcore voltage. In block 1008, the step count is set equal to zero. Inblock 1010, a conversion iteration is set equal to one. In block 1012,an input voltage is set equal to a voltage increment multiplied by thestep count. In block 1014, the internal nodes 315A-315N or similar ofthe system are pre-charged. In block 1016, the analog input 102 issampled. In block 1017, the held analog value is voltage shifted by theDC offset voltage and in block 1018, process waits for the conversiontime to expire. After the expiration of the conversion time, in block1020, the calculated error is set equal to the step minus the digitaloutput 108. In block 1022, the calculated error is converted ortranslated into a temperature and core voltage correction values. Thesecorrection values are stored for each conversion iteration and are laterused to calculate average correction values.

In block 1024, the conversion iteration number is compared to a maximumconversion number. In block 1024 if the conversion iteration is notequal to the maximum number, processing proceeds to block 1026. In block1026, the conversion iteration is incremented by one and processingproceeds back to block 1012 and continues to a next conversioniteration.

If in block 1024, the conversion iteration number is equal to themaximum number, then in block 1028, the compensation factors arecalculated as an average of the correction values for each iteration ofthe conversion processes. An independent compensation factors arecalculated for each set of temperature, core voltage and step value. Inblock 1030, the step, compensation factor, current core voltage andcurrent temperature values are stored in a memory for operationaltemperature and core voltage compensation.

In block 1032, the process determines if the step count is equal to2^(n)−1, i.e., the last step. In block 1032 if the step count is notequal to 2^(n)−1, then in block 1034, the step count is incremented byone and processing proceeds back to block 1010 for processing of thenext step value.

In block 1032 if the step count is equal to 2^(n)−1, then in block 1036,the process determines if the current core voltage is equal to themaximum operating core voltage. In block 1036, if the current corevoltage is not equal to the maximum operating core voltage, then inblock 1038, the current core voltage is incremented by the voltageincrement and processing proceeds back to block 1008.

In block 1036, if the current core voltage is equal to the maximumoperating core voltage, then in block 1040, the process determines ifthe current temperature is equal to the maximum operating temperature.In block 1040, if the current temperature is equal to the maximumoperating temperature, the process ends in block 1044. In block 1040 ifthe current temperature is not equal to the maximum operatingtemperature, then in block 1042, the current temperature is incrementedby the temperature increment and processing proceeds back to block 1006.In one aspect, the temperature and core voltage compensation factors arecomputed from an average value derived from multiple conversion cycles.In one aspect, only temperature compensation factors are generated. Inanother aspect, only core voltage compensation factors are generated.

In one aspect a system is provided. The system a plurality of flashcompare modules to output a set of unordered output signals based on ananalog input signal; a plurality of device selection modules thatreceive the unordered output signals and generate ordered signalsrepresenting the analog input; and a temperature and voltagecompensation module for receiving one or more of temperature and voltagesignals from at least a temperature and voltage sensor module thatsenses one or more of temperature and voltage values that are used tocompensate for changes in output signals caused by changes in one ormore of die temperature and core voltage.

In another aspect a system for analog to digital conversion is provided.The system includes a plurality of flash compare modules to output a setof unordered output signals based on an analog input signal; a pluralityof device selection modules that receive the unordered output signalsand generate ordered uncorrected thermometer encoded signalsrepresenting the analog input; a plurality of error correction modulesthat receive outputs from the plurality of device selection modules togenerate corrected thermometer encoded signals that are provided to athermometer to one-hot encoding module to generate one-hot encodedsignals; a state machine for controlling selection of outputs from theplurality of error correction modules; a binary encoding module toconvert the one-hot encoded signals into a digital output by a binaryencoding module; and a temperature and voltage compensation module whoseoutput is used to compensate for changes in one or more of dietemperature and core voltage compensation in an analog value to thedigital output.

In yet another aspect, a system for analog to digital conversion isprovided. The system includes a plurality of flash compare modules tooutput a set of unordered output signals based on an analog inputsignal; a plurality of device selection modules that receive theunordered output signals and generate ordered uncorrected thermometerencoded signals representing the analog input; a selection temperatureand voltage compensation module for receiving temperature and voltagesignals from at least a temperature and voltage sensor module thatsenses temperature and voltage values that are used to modifyconfiguration data used by the plurality of device selection modules forgenerating the ordered uncorrected thermometer encoded signals; aplurality of error correction modules that receive outputs from theplurality of device selection modules to generate corrected thermometerencoded signals that are provided to a thermometer to one-hot encodingmodule to generate one-hot encoded signals; a state machine forcontrolling selection of outputs from the plurality of error correctionmodules, where the state machine controls a multiplexer to timeinterleave outputs from the plurality of error correction modules; and abinary encoding module to convert the one-hot encoded signals into adigital output.

In another aspect, methods and systems are provided for circuits. Onemethod is for increasing device threshold voltage distribution of aplurality of devices of a circuit. The method includes adjusting adevice threshold voltage of the plurality of devices by differentamounts; and selecting a subset of the plurality of devices withadjusted device threshold voltage by a device selection module forperforming a function associated with the circuit.

In yet another aspect, a system for device threshold voltage adjustmentis provided. The system includes a sensor module for sensing one or moreof temperature and voltage values of a die having a plurality of devicesfor a circuit; and a threshold temperature and voltage compensationmodule for receiving an input value from the sensor module to compensatevariation in a device threshold voltage caused by changes of one or moreof temperature and voltage of the die.

In another aspect, a system is provided that includes an input samplingcircuit to capture an input signal value; a compare module that outputssignals based on the input signal value; a selection module thatarranges one or more outputs of the compare module; where the comparemodule includes one or more conversion devices with adjustable devicethreshold voltage values.

The various aspects described above may be implemented using circuitryand/or software modules that interact to provide particular results. Oneof skill in the computing arts can readily implement such describedfunctionality, either at a modular level or as a whole, using knowledgegenerally known in the art. For aspect, the flowcharts illustratedherein may be used to create computer-readable instructions/code forexecution by a processor. Such instructions may be stored on anon-transitory computer-readable medium and transferred to the processorfor execution as is known in the art.

The foregoing descriptions of the aspects have been presented for thepurposes of illustration and description. It is not intended to beexhaustive or to limit the inventive concepts to the precise formdisclosed. Many modifications and variations are possible in light ofthe above teaching. Any or all features of the disclosed aspects can beapplied individually or in any combination and are not meant to belimiting, but purely illustrative. It is intended that the scope belimited not with this detailed description, but rather determined by theclaims appended hereto.

What is claimed is:
 1. A device, comprising; an adjustment circuithaving an adjustable resistor for modifying a resistance value of aresistive device, the adjustment circuit connected to an adjustmentterminal of the resistive device; wherein the resistance value of theadjustable resistor changes, when a voltage or charge on the adjustmentterminal of the adjustable resistor is changed; wherein the adjustableresistor is a phase change element with an adjusting terminal to whichdifferent voltage values are applied for adjusting a conversion devicethreshold value.
 2. The device of claim 1, wherein the adjustableresistor is adjusted to compensate for any changes of one or more oftemperature and voltage.
 3. A device, comprising; an adjustment circuithaving an adjustable resistor for modifying a resistance value of aresistive device, the adjustment circuit connected to an adjustmentterminal of the resistive device; wherein the resistance value of theadjustable resistor changes, when a voltage or charge on the adjustmentterminal of the adjustable resistor is changed; wherein the adjustableresistor is a magneto-resistive element with an adjusting terminal towhich different voltage values are applied for adjusting a conversiondevice threshold value.
 4. The device of claim 3, wherein the adjustableresistor is adjusted to compensate for any changes of one or more oftemperature and voltage.
 5. A method for increasing device thresholdvoltage distribution of a plurality of devices of a circuit, comprising:adjusting a device threshold voltage of the plurality of devices bydifferent amounts; and selecting a subset of the plurality of deviceswith adjusted device threshold voltage by a device selection module forperforming a function associated with the circuit; wherein the devicethreshold voltage distribution is increased by adjusting manufacturingprocess parameters for the plurality of devices.
 6. A method forincreasing device threshold voltage distribution of a plurality ofdevices of a circuit, comprising: adjusting a device threshold voltageof the plurality of devices by different amounts; and selecting a subsetof the plurality of devices with adjusted device threshold voltage by adevice selection module for performing a function associated with thecircuit; wherein the device threshold voltage distribution is increasedby violating one or more of analog circuit design rules.
 7. The methodof claim 6, wherein device orientation is the violated analog circuitdesign rule.
 8. The method of claim 6, wherein guard ring isolation isthe violated analog circuit design rule.
 9. The method of claim 6,wherein locating the device in the proximity to other devices orstructures is the violated analog circuit design rule.
 10. The method ofclaim 6, wherein device matching is the violated analog circuit designrule.
 11. The method of claim 6, wherein minimizing parasitic seriesresistance is the violated analog circuit design rule.
 12. The method ofclaim 6, wherein constructing one or more of the plurality of devicesutilizing one or more identical units is the violated analog circuitdesign rule.
 13. The method of claim 6, wherein minimizing coupling of aplurality of lines within one or more of the plurality of devices is theviolated analog circuit design rule.
 14. A system for device thresholdvoltage adjustment, comprising; a sensor module for sensing one or moreof temperature and voltage values of a die having a plurality of devicesfor a circuit; and a threshold temperature and voltage compensationmodule for receiving an input value from the sensor module to compensatevariation in a device threshold voltage caused by changes of one or moreof temperature and voltage of the die; wherein extra devices areselected for the plurality of devices to compensate for one or morechanges to the device threshold voltage caused by changes in one or moreof temperature and voltage.
 15. A system for device threshold voltageadjustment, comprising; a sensor module for sensing one or more oftemperature and voltage values of a die having a plurality of devicesfor a circuit; and a threshold temperature and voltage compensationmodule for receiving an input value from the sensor module to compensatevariation in a device threshold voltage caused by changes of one or moreof temperature and voltage of the die; wherein input voltage scaling forthe plurality of devices is adjusted to compensate for one or morechanges to the device threshold voltage caused by changes in one or moreof temperature and voltage.
 16. The system of claim 15, wherein inputvoltage scaling is adjusted during manufacturing testing of theplurality of devices.
 17. A system for device threshold voltageadjustment, comprising; a sensor module for sensing one or more oftemperature and voltage values of a die having a plurality of devicesfor a circuit; and a threshold temperature and voltage compensationmodule for receiving an input value from the sensor module to compensatevariation in a device threshold voltage caused by changes of one or moreof temperature and voltage of the die; wherein to compensate for anychange to the device threshold voltage caused by changes in one or moreof temperature and voltage, device characteristics of the plurality ofdevices are characterized at a temperature and voltage different fromambient temperature and nominal voltage.
 18. A system for devicethreshold voltage adjustment, comprising; a sensor module for sensingone or more of temperature and voltage values of a die having aplurality of devices for a circuit; a threshold temperature and voltagecompensation module for receiving an input value from the sensor moduleto compensate for variations in a device threshold voltage caused bychanges of one or more of temperature and voltage of the die; and aselection module adjusts device selection to create a subset of theplurality of devices to compensate for changes in one or more oftemperature and voltage of the die; wherein a training sequence is usedfor selecting the subset of the plurality of devices.
 19. A system ofclaim 18, wherein the training sequence is performed on a communicationslink.
 20. A system comprising: a plurality of devices of a circuit forperforming a function associated with the circuit; a compensationtemperature and voltage compensation module for receiving one or more oftemperature and voltage signals from at least a temperature and voltagesensor module that senses one or more of temperature and voltage valuesthat are used to compensate for changes in performing the functionassociated with the circuit caused by changes in one or more oftemperature and voltage.